A. It is thought that in frozen root-stocks free Ca-ions combine with pectin in middle lamella which correspondingly becomes hard owing to the formation of insoluble pectin compound. The auther affirmed that combined Ca can be extracted only in acetic acid fraction, while in alcohol fraction only free ions are extracted : B. Soybean plants were cultured in water media containing different levels of Mg, Ca and K, but not Na. Cation concentations of Mg ranged from 0.3 to 30 ppm and that of Ca and K from 1 to 300 ppm. The samples harvested during the flowering period and dried were extracted with 70% alcohol and then with 2% acetic acid. Mg, Ca and K in each fraction were quantitatively analyzed. The results obtained may be summarized as follows : (1) The reciprocal relationship among Mg, Ca and K was not so distinct in alc. -fraction, but very significant in HAc-fraction, i. e. the increase of one of the cations as nutrient caused the increase of that cation in plants and the decrease of the other two, and the sum of chemical equivaents of the three cations was kept almost constant. (2) On the Ca-series, with the increase of Ca nutrient, HAc-sol. -Ca increased more distinctly than alc. -sol. -K was much lager than that of HAc-sol. On the Mg-series, the increase of Mg were almost equal in two fractions. (3) It is suggested that, as a ion substitutes for another cations combining with negative colloid like pectin and protoplasma, K-ion does not easily combine with it, while Ca-ion easily substitutes for another cations. So in the plant tissue a great part of K is in ionized condition and Ca is mostly in combined condition. (4) Furthermore these facts may relate to the state of protein in protoplasma and pectin in middle lamella. In the case of Ca-deficiency pectin in the middle lamella of the cell wall may be in sol-state, so the tissue of leaf and stem may gelatinize and weaken, while outwardly Ca-deficiency symptom appears : petioles and stems collapse (Photo. 1) and the plant easily lodges. In the case of K-deficiency pectin may become gel, so the plant becomes brittle and buckling may occur.
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